BUILD registration opened earlier today. The conference will take place in San Francisco April 2-4.

Last weekend, Microsoft watcher and blogger Paul Thurrott, citing anonymous sources, said the Redmond, Wash. company would outline its plan for Windows 9 at BUILD, and has set April 2015 as a preliminary target for shipping the upgrade to the perception-plagued Windows 8.

While Thurrott provided no additional detail about how the company envisioned Windows 9 -- previously, reports had circulated that Microsoft would restore a Start menu to the "classic" desktop and make it possible for "Metro" apps to run on the desktop -- he cast the upgrade as a make-or-break move and said Microsoft would use the "9" label to put some distance between it and its predecessor.

Microsoft pegged the free October 2013 update as "Windows 8.1," and most analysts expected that naming convention to last for at least one more iteration before the company moved on.

"The numbers are all a game," said Michael Silver, an analyst with Gartner who tracks Microsoft. "Who's to say Windows 9 will really be a magnitude difference? [The expected Windows 8.1 April 2014 update] is a spring update? Not a point release, not a service pack? The number is really in the eyes of the beholder and ultimately artificial."

But Silver acknowledged that an April 2015 release, rather than later in the year as has been Microsoft's general practice, had some logic behind it.

"People have criticized Microsoft for launching [new] Windows in the fall because that misses back-to-school," said Silver, referring to the surge in sales of traditional PCs, mostly notebooks, during the summer to students entering college or starting high school. "They need to get [Windows 9] out by April for back-to-school, so that's not a bad time of the year, as there's an opportunity for sales."

And Microsoft probably does want to leave behind the Windows 8 name, as Thurrott claimed.

"They may well want to get the '8' out of people's minds," Silver said, but he cautioned against expecting too much. Windows 7, he said, was generally perceived as a major change from Vista, Microsoft's 2007 flop, but he argued that Windows 7 was actually much less. "They polished up [Vista] and packaged it better [to make Windows 7]," Silver said. "Was it a major step forward? No."

Wes Miller of Directions on Microsoft, a Kirkland, Wash. research firm that specializes in following Microsoft's moves, also chimed in on Windows 9.

"If people expect a return of focus on the desktop, they'll be sorely disappointed," Miller said of users who have declined to migrate to Windows 8, anticipating that Microsoft will reverse course in its strategy to deemphasize the desktop and push customers toward the "Modern," nee "Metro" user interface (UI) and its touch-based app model.

At 2014's BUILD, Miller hopes to get a feel for how far Microsoft will stray from that strategy. "If they do, it will be a recognition by Microsoft that the OS is struggling a little bit."

Miller's "a little bit" was much kinder than others' comments portraying Windows 8's shortcomings. Even Thurrott, normally bullish on Microsoft, hammered the 2012 operating system, arguing that it was "tanking," and a "disaster" that Microsoft had to remedy by backing off the push to Metro.

According to Internet measurement firm Net Applications, Windows 8's and 8.1's combined user share of all computers reached 10.5% in December 2013, and 11.6% of all those running a form of Windows. Those numbers were less than half those of Windows 7 at the same point in its post-launch career.

Windows 8 fought headwinds not of its making, as consumers dramatically slowed their PC purchasing, opting instead to spend their dollars -- and "computing" time -- on tablets and smartphones. But that macro trend of declining PC shipments will not disappear by 2015, forcing Windows 9 to face the same adoption obstacles.